Schröder, Andreas and Geisler, Reinhard and Elsinga, Gerrit E. and Scarano, Fulvio and Dierksheide, Uwe (2006) Investigation of a turbulent spot and a tripped turbulent boundary layer flow using time-resolved tomographic PIV. Experiments in Fluids, Vol.: 44 (2), pp. 305-316. Springer Verlag Berlin/Heidelberg. DOI: 10.1007/s00348-007-0403-2. ISSN 0723-4864 (PRINT) 1432-114 (ONLINE).
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In this feasibility study the tomographic PIV technique has been applied to time resolved PIV recordings for the study of the growth of a turbulent spot in a laminar flat plate boundary layer and to visualize the topology of coherent flow structures within a tripped turbulent flat plate boundary layer flow. The experiments are performed around (Re<sub>x</sub> )<sup>½</sup> ≈ 450 in a low speed wind-tunnel using four high speed CMOS cameras operating up to 5 kHz. The volume illumination required a multiple-reflection system able to intensify light intensity within the measurement volume. This aspect is deemed essential when a high-speed tomographic PIV system is applied in air flows. The particle image recordings are used for a three dimensional tomographic reconstruction of the light intensity distribution within the illuminated volume. Each pair of reconstructed three-dimensional light distributions is analyzed by 3D spatial cross-correlation using iterative multi-grid schemes with volume-deformation, yielding a correlated time sequence of three-dimensional instantaneous velocity vector volumes. The coherent structures organization is analyzed by 3D-vorticity and -swirling-strength iso-surfaces visualization. In both flow types streaks and hairpin-like or arch vortical structures are most prominent. The data giving insight into the role of these structures for the spatio-temporal arrangement of the wall normal flow exchange mechanisms, especially of the instantaneous Reynolds stress events Q2 and Q4. A description of different self-sustainable flow organizations based on modifications of the hairpin-vortex- and streak- models is given. Two preliminary results are essential: Self-sustainability of a coherent vortical structure depends on the possibility to entrain high momentum fluid, initially Q4. And, stream-wise swirl at the near-wall region of arch or hairpin-like vortices has been observed to be seldom.
|Additional Information:||published online: 13. October 2007|
|Title:||Investigation of a turbulent spot and a tripped turbulent boundary layer flow using time-resolved tomographic PIV|
|Date:||2 October 2006|
|Journal or Publication Title:||Experiments in Fluids|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 305-316|
|Publisher:||Springer Verlag Berlin/Heidelberg|
|ISSN:||0723-4864 (PRINT) 1432-114 (ONLINE)|
|Keywords:||turbulent boundary layer, high speed tomographic PIV, 4-D PIV|
|HGF - Research field:||Aeronautics, Space and Transport (old)|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||Aircraft Research|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L AR - Aircraft Research|
|DLR - Research theme (Project):||L - Flight Physics|
|Institutes and Institutions:||Institute of Aerodynamics and Flow Technology > Experimental Methods|
|Deposited By:||Ilka Micknaus|
|Deposited On:||27 Jul 2007|
|Last Modified:||14 Jan 2010 22:29|
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